SUNDERLAND: Estimating the number of eclipse visitors is a nightmare

Published at 7:31 pm, August 23, 2017 |

Updated at 7:56 pm, August 23, 2017

It’s nearly impossible to get a real pulse on exactly how many people showed up in eastern Idaho for the Great American Eclipse.

There were simply too many variables.

We have physical proof that campgrounds and hotels were packed, we know places like Yellowstone and Craters of the Moon were massively congested, and we even had reports from many, many church congregations that attendance went up the Sunday before the eclipse.

On the flip side, though, we had just as many people asking where the crowds were and many eclipse-related events were under-attended.

So were there hordes of visitors, or weren’t there?

Well, we have a couple of semi-official guesses.

Shortly after the event, the city of Idaho Falls released an estimate that 300,000 people had shown up for the eclipse.

City officials based their number off preliminary data from the Idaho Transportation Department that showed on Monday morning, some 3,500 cars were traveling northbound on Interstate 15 every hour before the eclipse. The city’s estimate assumed there were two to three people in every vehicle, and city officials guessed on the amount of time visitors were on the road. They then took that estimate, and assumed similar traffic on southbound I-15 from Montana and other east and west paths to the totality such as U.S. Highways 20, 26 and Idaho Highway 33.

Authorities also included an estimate of visitors who arrived by air from various local airports, since not every small airport tracks the total number of people coming in by plane.

So although that estimate makes some sense, it is clear that it is a very rough estimate based on many assumptions.

“The exact number of people was hard to answer before the eclipse, and it’s hard to answer now because there are so many variables involved,” Idaho Falls city spokeswoman Kerry Hammon said.

Late Tuesday night, ITD released updated data, but that also appears to be problematic.

ITD reports traffic counters near state borders counted 449,530 cars entering Idaho between Aug. 18 and Aug. 21. This was an increase of 71,140 cars during the same time last year. Based on this number, ITD estimates more than 160,000 visitors came from out-of-state for the event — but that number is statewide. The agency based its number on the change in traffic between 2016 and 2017 at border locations and then multiplied it by 2.5 people per average vehicle, minus 5 percent for the local traffic.

But there is a large difference between an estimated 160,000 visitors spread across the 312-mile path of the totality from Payette to Victor and the estimated 300,000 people just in the Idaho Falls area.

So which estimate is the more correct?

Some anecdotal evidence: There was a traffic jam on parts of I-15 for almost 24 hours in southern Idaho and northern Utah all day Monday and into Tuesday. Similar long-term jams were reported on I-15 northbound into Montana and into Wyoming. And traffic was heavier in east Idaho than elsewhere in the state. Based on that, the city’s estimate seems more plausible.

On the other hand — also based solely on anecdotal evidence — residents across eastern Idaho said they saw few crowds, and many complained about over-hype and poor restaurant and retail sales right up until the eclipse. That would seem to suggest ITD’s number is closer to the truth.

I doubt we’ll ever know the exact number of people who visited last weekend, due to the sheer number of variables and the fact that counting every visitor or measuring how long they were here is impossible.

In the end, it probably doesn’t matter all that much. Thanks to lots of preparation by hundreds of people, everything went smoothly and it was a thoroughly enjoyable event.